"When you install macOS High Sierra on the built-in solid-state drive (SSD) of a Mac, that drive is automatically converted to APFS. Fusion Drives and hard disk drives (HDDs) aren't converted. You can't opt out of the transition to APFS."

About 4K, HDR, and Dolby Vision on your Apple TV 4K (new)
(Also see footnote about HDR10 and Dolby Vision refresh rates. Some TVs (like 2016 LG OLEDs) don't support 4K/UHD Dolby Vision at 60Hz and Apple TV doesn't support 24Hz, so 30Hz would be used - or 25Hz for PAL TVs. (In those cases Apple recommends 1080P at 60Hz/50Hz instead, for UI performance reasons.) Not sure why they don't just play the video/movie at 24P (source rate) and revert back to 60P when done. (And ditto for audio bitstreaming - I know they want to mix in their Interface sounds and Siri (resulting in LPCM), but during movie playback, why not allow a bitstream option? (On many people's wish list.)Update - reportedly Apple favors refresh rate over all else and considers mode switching (24Hz for movies, 60Hz or Interface) as "Inelegant", so everything runs at 60Hz (or 50Hz or PAL TVs). And for TVs like the 2016 LG OLED models that support Dolby Vision at up to 30Hz (not 60Hz), Apple TV 4K will use HDR10 mode (at 60Hz) instead. Why not give the user a choice? I think 2016 LG owners would prefer an option to watch the movie in 4K/UHD Dolby Vision (dynamic HDR) rather than (static) HDR10, even if the initial change to 24Hz caused a short display flicker/re-sync. Otherwise, is 1080/60P DV from Apple TV possible? (The TV will upscale 1080P to UHD.)Update 2 - Early owners report that under "Other Formats" there are 4K options for 24Hz HDR, 24Hz SDR and when connected to a Dolby Vision compatible TV, 24Hz Dolby Vision.
Apple's doc recommends cables with a "Dolby Vision mark" (tested with 4K Apple TV they say). Their example 2M Belkin Ultra High Speed cable is $29.95 at Apple's store and the specs list "up to 48 Gbps" - that's the (future) HDMI 2.1 spec rate. (The Apple TV 4K's specs show an HDMI 2.0a port - which is up to 18Gbps. I don't know of any retail HDMI 2.1 spec products yet. Hopefully a 4K Apple TV teardown shows what chip they're using.)
I've never seen a 'Dolby Vision' marked (or 48Gbps) HDMI cable (yet), but for current HDMI 2.0x 4K/UHD HDR/DV, a (HDMI 2.0x/18GHz) Certified Premium HDMI cable (6ft/as short as possible) worked reliably with a 4K/UHD HDR10 60P movie disc - Billy Lynn's Long Halftime Walk. (The only UHD/60P movie disc to date and a good stress test for cables, as other HDR10 and all DV discs to date are 24P.) IMHO Apple should have included a cable. (Some 4K UHD Players do, as it helps minimize returns due to cable related problems.) 6ft Certified Premium HDMI 2.0/18Gbps cables are under $10 retail at some sellers. There's also a free HDMI Premium Cable Authentication App to verify the code on the box label.)

Mac:
The new iTunes focuses on music, movies, TV shows, podcasts, and audiobooks. It adds support for syncing iOS 11 devices and includes new features for -

Apple Music. Now discover music with friends. Members can create profiles and follow each other to see music they are listening to and any playlists they've shared.

Podcasts. iTunes U collections are now part of the Apple Podcasts family. Search and explore free educational content produced by leading schools, universities, museums, and cultural institutions all in one place.

If you previously used iTunes to sync apps or ringtones to your iOS device, use the new App Store or Sounds Settings on iOS to redownload them without your Mac."

v05.30.03 Software Update for LG 55/65B6P OLED UHD TV
(Change info from page's "Reference" link, which has other (LCD) models listed also.)
1) Added notification pop up for when app is no longer supported.
2) Change in background image of no signal screen
3) Change in Amazon HDR mode
Although not listed, some reported HLG HDR support based on test file playback.
FYI: v05.30.0x update for C/E series had dimmer HDR Game Mode (see July archive).
And some say this update raised black levels. (Slight glow even with brightness at 0.)
(Link is for LG US D/L page if update does not appear using TV update check.
Update version numbers can vary by region - above is US version posted Sept. 9th.)